<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./vue.js"></script>
    <style>
        .box{
            width: 100px;
            height: 100px;
            background-color: pink;
        }
        .newbox{
            width: 100px;
            height: 100px;
            background-color: yellowgreen;
        }
    </style>
</head>
<body>
    <div id="app">
       <div>num:{{ num }}</div>
       <div :class="classname"></div>
       <button @click="fn(11)">点击num=11</button>
    </div>
    <script>
        var vm =  new  Vue({
            el:"#app",
            data:{
                num:10,
                classname:"box"
            },
            methods: {
                fn(b){
                    // console.log(b);
                    // 获取data中的属性值
                    console.log(this.num);  //10
                    // 设置data中的属性值
                    this.num = b;
                    this.classname = "newbox"
                }
            },
        })
    </script>
</body>
</html>